Flexible List Management in a Directory. H. V. Jagadish, Mark A. Jones, Divesh Srivastava and Dimitra Vista. Lists of entities must often be specified in many real-world applications such as customer lists, electronic distribution lists and access control lists. These lists are typically specified through explicit enumeration, frequently aided by recursive expansion. In this paper, we discuss the declarative specification and extraction of members of such lists as queries over a directory that maintains information both about individuals and about lists, and identify key features that the directory must support to manage lists in a flexible manner. X.500 is the industry standard for modeling information about individuals in a directory, and LDAP is the proposed standard for accessing directory information. We have designed and built a system to represent and manage lists in the X.500 information model, and developed efficiently evaluable extensions to the LDAP query language for the location and expansion of lists. We describe the system architecture and the query evaluation algorithm of this system. Our system is deployed for use in the specification and expansion of (organizational and personal) electronic messaging (e-mail, voice mail and FAX) distribution lists at AT&T Labs.